Punta Sur - Devil's Throat

The boat runs south for longer than it does to anywhere else on this coast, and the captain makes the call that morning, because the southern tip faces the trades and if they are up nobody dives it. At the end of the run there is a sand plateau beside the wall at 24 to 27 m, and a hole in the coral that looks like nothing at all until you are directly over it.

Groups settle on the sand and sort out their trim before anyone goes near the entrance. Then you go in single file behind the guide, spaced, into a shaft that drops at roughly 45 degrees and squeezes to about a metre and a half in one section. It darkens fast, and then the blue light at the far end appears. Sixty to ninety seconds is the whole of it. Deep red and orange sponge coats the walls, and at this depth daylight has no red left in it, so that colour exists only inside a torch beam. One technique is not negotiable: frog kick, because a flutter kick in a passage this narrow silts out everyone behind you. Whether to go feet first or head first is genuinely unsettled, so take the route the guide briefs on the day.

Then the exit, which is the dive. You come out of the reef into open water between 35 and 43 m, on a sheer wall, with the drop falling away beneath you and the surface a long way up. It lasts about a minute before the computer starts asking for the ascent.

The rest is that ascent, and operators run it differently. Some thread a series of shallower swim-throughs back up through the same mound and finish over a sandy slope at around 10 m. Others come back through the shallower sections of the reef to a stop near the top. Southern stingrays and sleeping nurse sharks are on those sandy stretches, glassy sweepers school in the darker chambers, and the shallow passages above the tunnel are, by several accounts, the better part of the coral head.

The number published for this dive is the wrong number, and getting it wrong has a cost. Most listings give a maximum around 27 m. That figure is the entry, the mouth of the shaft, and the dive continues down through it. Ten independent published descriptions put the exit between 35 and 43 m, most of them at 40, and divers' own logged maxima run 115, 118, 120, 123, 129 and 140 feet. Someone who plans for 27 m has planned for the ceiling of a dive whose floor is 13 m further down.

The spread has mechanical causes. Several passages run through this coral head above and below the main one, and which one the guide takes changes where you come out: one diver who went left surfaced from an exit around 140 feet. The exit is also where people wait, hovering in open water off the wall while the rest of the group files through one at a time, and hovering there costs depth. Below all of it the wall keeps falling, so there is no floor underneath to stop a slow drift downward.

Everything else this island sells is a reef or a wall you can move shallower on whenever you like. Here you are in a queue in a one-way passage, at a depth where a standard aluminium cylinder gives most divers well under ten minutes of no-decompression time. One diver described the geometry exactly: in the middle of the line, he realised he could go neither forward nor back. That arithmetic is the whole argument of the site, and it is also why the divers who know this island best are lukewarm about it. Plenty of them would rather dive the shallower swim-throughs over the top of the same coral head, and some decline the tunnel by choice and meet the guide again below the exit. Declining is briefed, ordinary, and costs you nothing except the story.

Nobody gets on this dive on the strength of a card. Operators ask for Advanced Open Water and then keep going: most want to have dived with you already and watched what your buoyancy and your consumption look like, one publishes a 50 logged dive minimum, and some will not run the site at all. An AOW card authorises 30 m, which is above the exit, so the training that actually fits the profile is a Deep Diver specialty. No cave or cavern certification is required by anyone. After all that the boat still has to agree, because everyone aboard has to want the dive and be able to do it, or the group goes somewhere else.

None of that is law. The park's rules accredit the guide and not the diver: an authorised guide must supervise every dive1, and the instrument sets no certification level for divers anywhere in it. What it does set here bites in other ways. This is the park's most restricted zone and it names Punta Sur in its own text: six divers per guide instead of eight, an outright ban on night diving, and a 45 m ceiling on sport diving that the deepest published exit sits two metres inside1. The park also rests reefs in rotation and can close this complex, so ask your dive shop which reefs are resting for your dates; no government page publishes the year's calendar.

Leave nitrox alone unless the shop can blend for the profile. EAN32 is the standard island fill, its maximum operating depth at a PO2 of 1.4 is 33.8 m, and that is roughly six metres above the modal exit. The intuition that a deeper dive wants a richer mix is exactly backwards here.

Then the things that decide how the dive goes. Take a proper primary light, not the backup in your pocket, since every operator that publishes a kit list requires one and the sponge colour is the only reason the passage is worth looking at. Gas is what people underestimate, so work out beforehand what it would take to leave the overhead and reach the surface sharing air, and ask which cylinder you will be handed, because steel 100s and 120s are the local answer to this site. Ask the group size too: a queue of twelve at 27 m spends your gas before you enter the tunnel. And say the words, because boats sell the reef and the tunnel both as Punta Sur. Name the Devil's Throat if you want it, and say so plainly if you do not.